1. Field of the Invention
The present invention relates to a liquid container that utilizes negative pressure for supplying liquid to the outside. The invention also relates to a liquid supply system and a method for manufacturing such liquid container.
2. Related Background Art
As disclosed in the specification of Japanese Patent Application Laid-Open No. 9-267483 filed by the applicant hereof, there has been known conventionally the ink tank having ink contained in an area (hereinafter referred to as an ink containing portion) surrounded by the inner walls which are separable from the outer walls that form the outer enclosure thereof.
The inner walls of the aforesaid ink tank are formed sufficiently thicker than the outer walls so that the outer walls present almost no deformation even when the inner walls are deformed by the outflow of ink contained therein. Also, the air intake is provided for the outer walls to induce the air into the gap between the outer walls and the inner walls. For the inner walls, the welding portions (pinch offs) are provided to support the inner walls by the welding portions to enable them to engage with the outer walls.
For the ink tank thus structured, the force exerted by the deformation due to the consumption of ink acts upon the inner walls thereof, together with the force that may be exerted by the restoring action thereof to return its shape to the initial state. This contributes to making negative pressure more stable in the ink container, and also, making the ink tank excellently functional in utilizing such stabilized negative pressure while supplying liquid.
Also, in the specification of the aforesaid Japanese Patent Laid-Open Application, it has been disclosed that the inner and outer walls of the ink tank are structured with multiple layers of different materials in order to enhance its shock resistance.
Now, a printer is often used under the environment having a specific temperature, although the use environment of a printer in general differs greatly depending on the regions where it is used.
In actual cases, there is a region where the temperature is considerably changeable or a region where the temperatures are considerably different even in a day. Here, the inventors hereof have found that the negative pressure changes even when the degree of deformation is the same if the ink tank is used in a condition where the temperatures may change as described above. Then, it is also known that even with an ink tank which is capable of demonstrating the desired characteristic of negative pressure at a certain specific temperature, there is a possibility that such desired characteristic of negative pressure becomes unobtainable due to its fluctuation that may be caused by the environmental condition where the temperature changes greatly against the temperature thus set specifically. In this case, there is a need for the adjustment of negative pressure, such as increasing the frequency of recovery process more than usual so that the ink leakage is prevented from the recording head when printing is made under such environment that its temperature is caused to differ greatly from the one thus set specifically.
Therefore, the inventors hereof have studied assiduously to ascertain the causes in this respect, and succeeded in obtaining the new knowledge that there is an important relationship between the elastic moduli of resin used as the material of the inner walls, which may change due to the temperature changes, the temperature at the glass transition point (that is, the temperature at which molecules begin micro-Brownian motion and the characteristic changes from glass to rubber), and the temperature of use environment.
Also, since the ink tank contains ink or some other liquid in it, the ink tank should be made to present an excellent liquid contactness with ink (that is, it does not affect the composition of ink when it is in contact with ink), and also, present an excellent gas barrier capability. However, these functional resins are generally subjected to being peeled off from each other thus making it necessary to provide a bonding layer between them in order to bond the resin layers firmly with each other.
On the other hand, the ink tank, which has been disclosed in the aforesaid specification of Japanese Patent Laid-Open Application, is manufactured by expanding a cylindrical parison in the mold the section of which is square column so that the ink tank has a thickness distribution. As a result, when the inner walls should be formed with multiple layers, the central part of each layer is made relatively thicker than each of the corner portions, thus making the thickness distribution to change smoothly from the central portion to the corners eventually. As a result, if the contact layers should be provided in order to allow the multiple layers to be in contact reliably with each other, the thickness of the contact layers increases inevitably centering on the central portion, which makes the thickness larger for the inner walls as a whole.
Now, therefore, the present invention is designed with a view to solving the problems discussed above. It is an object of the invention to provide a liquid container capable of implementing the stable supply of liquid by stabilizing the characteristic of negative pressure irrespective of the temperature changes of use environments, and also, to provide a liquid supply system and a method for manufacturing such liquid container as well.
In order to achieve the objects described above, the liquid container of the present invention comprises the inner wall that forms the liquid containing portion to contain liquid therein; the outer wall that forms the container to contain the liquid containing portion therein; and the liquid supply portion for supplying liquid from the liquid containing portion to the outside. Then, the aforesaid inner wall is arranged to be a member to generate negative pressure in the liquid containing portion by being deformed following the leading-out of the liquid, and formed by the material having the elastic modulus change of 25% or less against the temperature change of use environment.
In accordance with the liquid container of the present invention thus structured, it becomes possible to stabilize the characteristic of negative pressure irrespective of the temperature changes of the use environment whether the material of the inner walls is an amorphous resin or a crystalline resin.
Also, the liquid container of the present invention comprises the inner wall that forms the liquid containing portion to contain liquid therein; the outer wall that forms the container that contains the liquid containing portion therein; and the liquid supply portion for supplying liquid from the liquid containing portion to the outside. Then, the aforesaid inner wall is arranged to be a member to generate negative pressure in the liquid containing portion by being deformed following the leading-out of liquid, and formed by an amorphous resin material having a higher glass transition temperature than the maximum temperature of use environment.
Also, the liquid container of the present invention comprises the inner wall that forms the liquid containing portion for containing liquid therein; the outer wall that forms the container that contains the liquid containing portion therein; and the liquid supply portion for supplying liquid from the liquid containing portion to the outside. Then, the aforesaid inner wall is arranged to form a multiply layered structure comprising an oxygenproof permeable layer, a resistive layer against the environmental change of temperature, and a liquid resistance layer. Then, the liquid resistance layer is provided for the innermost layer which is in contact with the liquid. The resistive layer against the environmental temperature change is formed by an amorphous resin having a higher glass transition temperature than the maximum temperature of use environment. Then, the inner wall is structured to generate negative pressure in the liquid containing portion by being deformed following the leading-out of liquid.
Since the amorphous resin has almost a constant elastic modulus at the temperatures lower than the glass transition temperature thereof without being affected by them then, it is possible to stabilize the characteristic of negative pressure if the inner walls are formed by an amorphous resin material having a higher glass transition temperature than the maximum temperature of the use environment, hence implementing a stable supply of liquid irrespective of the temperature changes of the use environment.
Further, the resistive layer against the environmental temperature change of the inner wall is provided between the liquid resistance layer and the oxygenproof permeable layer. At the same time, this layer may be structured to contain a functional bonding resin material or it may be possible to provide the oxygenproof permeable layer between the liquid resistance layer and the resistive layer against the environmental temperature change, and to contain a functional bonding resin material in this layer.
In this manner, the outermost layer and the innermost layer that form the inner walls are integrally formed together with the intermediate layer to which the functional bonding resin material is added to suppress increasing the thickness of the inner walls as compared with those produced by the conventional art in which the bonding layers are arranged, hence making the changes of negative pressure smoothly.
Also, the resistive layer against the environmental temperature change of the inner wall may be structured to provide the elastic modulus of 15% change or less along the temperature change of the use environment.
Further, this layer may be arranged to be installed in the container of the negative pressure generating member which is capable of creating the gas-liquid exchange that may lead out liquid by inducing gas into the liquid container through the liquid supply portion.
Also, the liquid supply system of the present invention is provided with the container of a negative pressure generating unit capable of creating the gas-liquid exchange that may lead out liquid by inducing gas into the liquid container through the liquid supply portion.
Since the liquid container of the present invention can stabilize the characteristic of negative pressure irrespective of the temperature changes of the use environment, it becomes possible to reduce more the buffer space to be arranged in the container of the negative pressure generating member by structuring the liquid supply system using this liquid container.
Further, the structure may be arranged so that the liquid container is detachably mountable on the container for the negative pressure generating member.
Also, the method of the present invention for manufacturing the liquid container, which is provided with the inner wall that forms the liquid containing portion to contain liquid therein, the outer wall that forms the container that contains the liquid containing portion therein, and the liquid supply portion for supplying liquid from the liquid containing portion to the outside, comprises the steps of preparing a mold corresponding to the outer contour of the liquid container, a substantially cylindrical first parison having a diameter smaller than that of the mold for use of the outer wall, and a second parison for use of the inner wall; and forming the outer wall and the inner walls of the liquid container by injecting the air inside to expand the first and second parisons to follow the mold so as to make the area formed by the inner wall and the area formed by the outer wall separable and substantially analogous. Then, the step of preparing the second parison for use of the inner wall comprises the step of preparing a multiply layered structure containing an oxygenproof permeable layer, a resistive layer against the environmental temperature change, and a liquid resistance layer.
In this manner, it is possible to implement a stable liquid supply with the stabilized characteristic of negative pressure irrespective of the temperature changes of the use environment.
Further, it may be possible to arrange the step of preparing the second parison for use of the inner wall to comprise a step of forming the second parison to be provided between the resistive layer against the environmental temperature change and the oxygenproof permeable layer, and a step of containing a functional bonding resin material in the resin that forms the resistive layer against the environmental temperature change or it may be possible to arrange the step of preparing the second parison for use of the inner wall to comprise a step of forming the second parison to be structured so as to provide the oxygenproof permeable layer between the liquid resistance layer and the resistive layer against the environmental temperature change, and a step of containing a functional bonding resin material in the resin that forms the oxygenproof permeable layer.
Further, it may be possible to form all the layers with a material that mainly contains ethylene or propylene as the skeletal structure thereof. Then, it becomes possible to manufacture a liquid container, while suppressing the increase of the thickness of the inner walls unlike the conventional art which necessitates the provision of bonding layers for bonding the innermost layer, the intermediate layers, and the outermost layer together.